Single-frequency InAsSb lasers emitting at 3.4 μm

Abstract

Single frequency InAsSb lasers operating from 77 to 110 K in CW mode have been tested for their suitability for trace gas analysis. The threshold current I th was as low as 25 mA at 78 K with a characteristic temperature T 0 of 25 K. Selected lasers show single-frequency operation over a large range of currents and temperatures with a side mode suppression ratio of 25 dB. The FWHM of the far-field pattern was 30 and 50 degrees in lateral and transverse directions, respectively. The beam elliptical factor was 1.7. The maximum CW optical power was up to 1.2 mW per facet to single frequency at 80 K. The lasers allowed tuning by the injection current without mode hopping of about 1.2 cm −1 with a tuning rate of 0.032 cm −1 mA −1. The average temperature tuning was 1.3 cm −1 K −1. Relative intensity noise in normal operation was as low as 4 × 10 −16 at 1 Hz. Therefore, a theoretical detection limit in terms of optical density of 2 × 10 −8 has been estimated for measurements by tunable diode laser spectroscopy at 3.4 μm.